1. Field of the Invention
The present invention generally relates to a intruder detecting method and an apparatus for detecting a intruder invading an detection area defined in, for example, a window, entrance or apron region in front of one or more wall-mounted paintings.
2. Description of the Prior Art
In the practice of a method of detecting and alarming intruder or approach into an detection area of a human body such as that of an invader through a window, entrance or fence of a dwelling house or warehouse or through a wall of the warehouse likely to be invaded by boring the wall, or that of a person approaching valuable paintings, it has been known to use a magnet switch, an infrared beam sensor used outdoors, or a passive type infrared (PIR) sensor used indoors adjacent the window.
FIG. 16 illustrates one of exemplary methods of detecting the intruder with the use of a magnet switch. In this example, of a magnet 52 and a reed switch 53 both constituting a magnet switch 51, the magnet 52 is fitted fixedly to a movable member such as a window 55 or a door 56 of, for example, a house 54 while the reed switch 53 is fitted fixedly to a stationary member such as a window sash or a door sash. This intruder detecting method makes use of closure or opening of the reed switch 53 that is brought about by increase or decrease of the spacing between the magnet 52 and the reed switch 53 in response to selective opening or closing of the window 55 or the door 56, respectively.
FIG. 17 illustrates one of exemplary methods of detecting the intruder with the use of the active infrared beam sensor. In this example, a light emitter 59 and a light receiver 60 altogether constituting the infrared beam sensor 58 are so installed at opposite ends of an outdoor side of a house 54 so as to allow a near infrared beam 57, emitted from the light emitter 59, to traverse in front of a window 55 and a door 56, wherefore when the near infrared beam 57 is intercepted by a intruder, the light receiver 56 can generate a detection signal. The infrared beam sensor 58 is featured in that a long distance monitoring is easy to achieve and in that it is hardly affected with change in ambient temperature, and is, therefore, often used for detection outdoors.
FIG. 18 illustrates one of exemplary methods of detecting the with the use of the PIR (Passive Infrared) sensor. In this example, the PIR sensor 61 is so configured and so installed inside a house 54 as to allow a single finger-like detection area 62 to traverse inwardly of a window 55 and a door 56 of the house 54, so that far infrared rays of light emitted by a intruder traversing the detection area 62 can be detected by the PIR sensor 61. Since the PIR sensor 62 is a sensor utilizing the principle of detection of a intruder in terms of change in temperature within the detection area, it is often used indoors to avoid any possible erroneous operation which would be triggered by an outdoor source of heat such as, for example, sunlight or automobiles.
FIG. 19 illustrates another example of the methods of detecting the intruder with the use of the PIR sensor. In this example shown in FIG. 19, the PIR sensor 61A is so configured and so installed inside a house 54 so that an area inwardly of a wall of the house 54 including a window 55 and a door 56 can be covered by a curtain-shaped detection area 63 that extends in a fashion similar to a curtain continuously in both vertical and horizontal directions, wherefore far infrared rays of light emitted by a intruder traversing the curtain-shaped detection area 63 can be detected by the PIR sensor 61A.
FIG. 20 illustrates a further example of the methods of detecting the intruder with the use of the PIR sensor. In this example, the PIR sensor 61B is so configured and so installed inside a house 54 that an area inwardly of a wall of the house 54 including a window 55 and a door 56 can be covered by a plurality of finger-like alert bands developing in a multi-staged pattern in a vertical direction to form a semi-curtain-shaped detection area 64 having a coverage generally equal to that of the curtain-shaped detection area 63, shown in FIG. 19, wherefore infra infrared rays of light emitted by a intruder traversing the semi-curtain-shaped detection area 64 can be detected by the PIR sensor 61B.
In the intruder detecting method using the magnet switch 51 as shown in FIG. 16, no intruder can be detected unless the spacing between the movable member such as the window 55 or the door 56 and the stationary member varies. Accordingly, no intruder can be detected in the event that a intruder cuts, for example, a windowpane of the window 55 to form a hole at a location remote from the site of installation of the magnet and then invades the house 54 through the hole in the windowpane. Also, with this intruder detecting method, the magnet switch 51 is required and must be installed for each of the windows 55 and the doors 56 and, therefore, if the house 54 or any other building has relatively many windows 55 and doors 56, complicated and time-consuming electric wiring is required, resulting in increase of the const for installation of the intruder detecting system.
In the intruder detecting method using the active infrared beam sensor 58 as shown in FIG. 17 wherein the near infrared beam 57 traverses in front of the window 55 and the door 56, the use of the single infrared beam sensor 58 is sufficient even where the house 54 has pluralities of windows 55 and doors 56 and, therefore, as compared with the method in which the magnet switches 51 are used, the labor required for installation of the requisite electric wiring can be considerably reduced. However, this method shown in FIG. 17 requires the near infrared beam 57 to extend linearly in front of the window 55 and the door 56, the use of the light emitter 59 for emitting the near infrared beam 57 and the light receiver 60 for receiving the near infrared beam 57 requires an accurate adjustment of the optical axis to allow the light emitter 59 and the light receiver 60 to be optically aligned with each other. Therefore, if the light emitter 59 and the light receiver 60 are spaced a substantial distance from each other, two attendant worker would be required to accomplish the requisite optical alignment adjustment, resulting in time-consuming and cumbersome labor.
Also, since in the case of this intruder detecting method, the detection area extends substantially in a line, the possibility exists in which if a intruder can locate the position at which the near infrared beam 57 travels across the window 55, the intruder will find no difficulty managing to intrude into the house through the window 55 without intercepting the near infrared beam 57 particularly where the window 55 is relatively large. To avoid this possibility and, hence, in order for this intruder detecting method to work effectively, the use of a plurality of parallel near infrared beams 57 in a staged fashion would be essential and, in such case, the number of jobs to be repeatedly performed for the optical alignment adjustment will consequently increase, resulting in a further increase of the amount of labor required.
The intruder detecting method employing the PIR sensor 61, 61A or 61B shown in FIGS. 18, 19 or 20 requires the PIR sensor 61, 61A or 61B to be merely installed at one side leftwards or rightwards of the opening and does not require a job to be performed for the optical alignment adjustment discussed above and, therefore, installation is easy and simple to accomplish. However, this intruder detecting method works to provide the intruder detection signal indicative of an unauthorized entry into the house only when and after a intruder has entered the house. Accordingly, this intruder detecting method is ineffective in that it can no way satisfy the user's requirement that a possible intruder should be detected before a potential intruder enters the house and/or that the windowpane of the window 55 should not be broken by a potential intruder.
In the example where the detection area 62 is of a finger-like shape as shown in FIG. 18, once the position at which the detection area 62 traverses is located in a manner similar to that in the case where the near infrared beam sensor 57 is employed as shown in FIG. 17, the possibility exists that a potential intruder will find no difficulty managing to intrude into the house through the window 55 without traversing the detection area 62.
Where the PIR sensor 61A or 61B are installed so that the curtain-shaped detection area 63 or the semi-curtain-shaped detection area 64 is oriented downwards as shown in FIG. 19 or 20, respectively, the possibility may exist that the PIR sensor 61A or 61B may erroneously detect a small size animal such as a rat or pet as a intruder. Where the PIR sensor 61A or 61B shown in FIG. 19 or 20, respectively, is installed outdoors so that the detection area 63 or 64 can be oriented upwards, the possibility of erroneous operation resulting from the presence of the small size animal may be eliminated, but a similar erroneous operation will occur under the influence of an external disturbance light such as sunlight or the like.